Don't assert when redefining a built-in macro in a PCH, PR29119

PCH files store the macro history for a given macro, and the whole history list
for one identifier is given to the Preprocessor at once via
Preprocessor::setLoadedMacroDirective(). This contained an assert that no macro
history exists yet for that identifier. That's usually true, but it's not true
for builtin macros, which are created in Preprocessor() before flags and pchs
are processed. Luckily, ASTWriter stops writing macro history lists at builtins
(see shouldIgnoreMacro() in ASTWriter.cpp), so the head of the history list was
missing for builtin macros. So make the assert weaker, and splice the history
list to the existing single define for builtins.

https://reviews.llvm.org/D27545


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@289228 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 35 insertions, 0 deletions

diff --git a/test/PCH/builtin-macro.c b/test/PCH/builtin-macro.c
new file mode 100644
index 0000000000..4d0154023e
--- /dev/null
+++ b/test/PCH/builtin-macro.c
@@ -0,0 +1,35 @@
+// Test this without pch.
+// RUN: %clang_cc1 -D__DATE__= -D__TIMESTAMP__= -include %s -Wno-builtin-macro-redefined -fsyntax-only -verify %s
+
+// Test with pch.
+// RUN: %clang_cc1 -D__DATE__= -D__TIMESTAMP__= -Wno-builtin-macro-redefined -emit-pch -o %t %s
+// RUN: %clang_cc1 -D__DATE__= -D__TIMESTAMP__= -Wno-builtin-macro-redefined -include-pch %t -fsyntax-only -verify %s 
+
+#if !defined(HEADER)
+#define HEADER
+
+#define __TIME__
+
+#undef __TIMESTAMP__
+#define __TIMESTAMP__
+
+// FIXME: undefs don't work well with pchs yet, see PR31311
+// Once that's fixed, add -U__COUNTER__ to all command lines and check that
+// an attempt to use __COUNTER__ at the bottom produces an error in both non-pch
+// and pch case (works fine in the former case already).
+// Same for #undef __FILE__ right here and a use of that at the bottom.
+//#undef __FILE__
+
+// Also spot-check a predefine
+#undef __STDC_HOSTED__
+
+#else
+
+const char s[] = __DATE__ " " __TIME__ " " __TIMESTAMP__;
+
+// Check that we pick up __DATE__ from the -D flag:
+int i = __DATE__ 4;
+
+const int d = __STDC_HOSTED__; // expected-error{{use of undeclared identifier '__STDC_HOSTED__'}}
+
+#endif